The present invention refers to a dynamic fluid device.
Use of hydraulic pumps with a fixed flow rate to feed user device of the same machine is well known and, in order for each one of them to work, they require a predefined flow of pressurised fluid which is oil in this specific case.
Hydraulic pumps with a fixed flow rate have the advantage of being considerably more economical than those with a variable flow rate which are also known and widely used.
One example of where these pumps are installed is on agricultural machines: they have hydraulic systems that feed main and secondary functions.
By the term main functions it is understood those functions the machine needs to move safely, for example, hydraulic powered steering, while by the term secondary functions it is understood those operating functions machines can be equipped with for working, for example, a hydraulic lifting equipment, a bucket and the like.
To feed all the user devices, the pumps with a fixed flow rate must be sized to guarantee a sufficient flow of pressurised oil under the heaviest conditions, i.e. when a great number of the primary and secondary devices are being used simultaneously.
When this does not occur, i.e. when only one user device is used, the pump, sized to supply a flow to meet the heaviest conditions, continues to supply the same flow of pressurised oil which becomes noticeably much more than what is really needed to operate a single user device; consequently, a large part of the pressurised oil flow supplied by the pump is superfluous and, for this reason, sent to a discharge point of the hydraulic system provided for.
This situation leads to a useless consumption of energy to be supplied to the pump for it to work and an anomalous heating of the pressurised oil, due to the fact it is not all used.
To solve these drawbacks, hydraulic circuits are used equipped with two pumps with a predefined fixed flow rate and arranged in parallel with each other; each pump is connected by a pipe to a single first user device and a single second user device.
An extension of the feed pipes is provided for at the output of both the first and second user devices that join together to flow into one single additional pipe which, in turn, is connected to a third user device; the sum of the flows of the single pumps when they are both working comes together in this one single additional pipe.
Nevertheless, a solenoid valve is mounted on one of the feed pipe extensions, before they join together, which opens or closes the extension it is mounted on, alternatively letting the flow of oil go through this extension to the third user device together with the flow of oil that goes through the parallel pipe of the other user means, or deviating the flow of the pipe extension on which it is mounted to a discharge way contemplated for this purpose in the hydraulic circuit.
In this way three user devices can be supplied with three different flows and the total value of the flow rates can be regulated with greater precision in line with the requirements of the user device being used, turning the pumps on or off as needed.
With this adjustment it is allowed to reduce the flow of pressurised oil to be discharged if all or part of it is not being used by one or more user devices.
A second known hydraulic system to supply user devices uses just one pump, normally a gear pump which, by means of a pipe, is connected to a distributor unit arranged to distribute pressurised oil “on demand” to a multitude of user devices.
The oil is distributed “on demand” in order to work one or more user devices and the request for oil is activated either by a manual operation of a user devices' driving unit mounted on a machine by an operator or by an automatic device arranged for this purpose on the distributor.
A valve is installed between the gear pump and distributor that connects the oil feeding pipe, adjusting the passage hole through which the oil flows to a discharge way.
The valve is controlled by pressure signals that reach it by way of a pressure detecting pipe which in technical jargon is called a “load-sensing line”; pressure is detected inside the distributor and transmitted to the valve which, according to the specific requirements of pressurised oil modifies the passage hole to the distributor and, hence, the available flow of pressurised oil to the user devices; when no signal is sent by the load-sensing line, the valve normally keeps the feed pipe connected to the discharge way and all the pump flow goes into it.
An additional requirement of agricultural machines and work vehicles in general that are fitted with a multitude of hydraulically controlled user devices, is that the feeding must be provided by the pumps according to an established priority, where the user devices that controls the machines main functions are supplied first followed by the user devices that control the secondary functions.
The state of the art described previously has a few drawbacks.
A first drawback is that the hydraulic circuits that have pumps with a fixed flow rate feeding single user device do not allow for priority in feeding such devices.
A second drawback is that if, in a hydraulic circuit which has two pumps in parallel with each other, one of the pumps is damaged, the user device being supplied by this damaged pump cannot work.
A third drawback is that if a third user device requires a reduced flow of pressurised oil to work compared to the flow rate just one of the pumps installed in parallel on the hydraulic circuit can supply, a significant quantity of pressurised oil has to be discharged and the energy spent to operate the pump, or both pumps, is lost.